As shown in FIG. 1, an existing LCD device includes a panel and a backlight module; the surface part and the bottom part of the panel are respectively provided with a color filter (CF) substrate and a thin film transistor (TFT) substrate, and the two glass substrates are respectively attached with a polaroid. Each polaroid has the function of selecting light so that light with the same polarization direction as that of the polaroid can pass through the polaroid. When the light of the backlight module is radiated to the lower polaroid, light with the same polarization direction as that of the lower polaroid passes through the lower polaroid; because liquid crystal in the panel has birefringent characteristics, the polarization direction of light is caused to deflect by different deflecting directions of the liquid crystal, and light is selected again when passing through the upper polaroid. The intensity of light emitted from the panel is controlled by the deflecting direction of the liquid crystal, and the polaroid is equivalent to a switch for filtering the polarization direction. Because only P light whose direction is the same as that of the polaroid can pass through the polaroid, accordingly, partial light can not pass through the polaroid, causing the brightness of an LCD device to be reduced, and the light energy to be wasted.
The U.S. Patent US20090185107 discloses a structure of a backlight module. In the invention, the light emergent surface of the backlight module is additionally provided with a lens structure. The lens structure can select P light to pass through a polaroid and reflect the rest light back to the backlight module. The light changes deflecting directions by being refracted and reflected by optical devices in the module and then passes through the lens structure. The light utilization rate can be increased by such repetition. However, the lens structure is complicated and has high manufacturing cost.